IT was once a fortification of fear for visiting teams from across Europe.
A bastion built on belief where the crowd was the 12th man and some of the continent’s biggest enemies were put to the sword.
Yet the walls have started to crumble around Celtic’s stronghold in recent seasons.
The Hoops have failed to win any of the last ten group games played at Parkhead in the Champions League and Europa League.
Granted, in that time they’ve faced the might of the likes of Manchester City, Barcelona, PSG and Bayern Munich.
But there’s no doubt the ground has lost some of its lustre as a place where a thunderous atmosphere could cause players to panic and world stars to wobble.
Brendan Rodgers’ men did, though, do enough to finish in third spot in their group in this season’s Champions League.
That set up a Europa League last-32 clash with Russian outfit Zenit St Petersburg next month.
The games are now back to being two-legged affairs — and keeper Craig Gordon reckons that will see Celts start to restore the walls around their castle.
They host Zenit in the first game on February 15, with the return trip a week later.
Gordon said: “We are going back to two-legged ties so we need to start winning at home.
“When the matches have been two-legged knockout games, in the qualifying campaigns over the last two seasons, we have done quite well.
“I think those ties have suited us. We have known how to deal with the pressures of the away goal situation.
“It also depends who is at home first because it can change how you approach the game and whether you are attacking or defending. There are a lot of things that come into play in knockout football which change things a little.”
French big-spenders PSG and German giants Bayern were the sides who qualified for the next stage of the Champions League from Celtic’s group.
The vast budgets of both dwarf the sort of money Rodgers can splash in the transfer market.
Instead he has to wheel and deal and try to uncover players looking to kick-start their career all over again or attempt to land youthful players searching for first-team opportunities.
Borussia Dortmund have joined Celts in the Europa League.
But the Germans’ plight alone shows the gap between the haves and the have-nots.
Their progress came despite earning just two points in a group which saw Real Madrid and Tottenham bulldoze their way to qualification.
Gordon said: “It can depend how your group pans out but more often than not the top two seeds go through.
“There are only one or two situations and groups where that hasn’t happened.
“You do expect those teams at the top level to qualify and it is a bit of a fight for the other ones to try to get into the Europa League.
“Occasionally you get the big names dropping into the Europa League and it is great for us to be involved in it.”
Incredibly Gordon, 35, has already played 42 games for club and country this term.
He signed off by making those crucial saves which kept Rangers at bay in Saturday’s goalless Old Firm derby draw.
The Hoops are on their winter break — with the squad re-assembling in Dubai this weekend for their training camp.
A spell working in the desert sunshine a year ago helped set them up for their Treble charge in the second half of last season.
With the transfer window open, German defender Marvin Compper has already joined from Red Bull Leipzig.
St Mirren winger Lewis Morgan is also on the brink of signing, although he will spend the second half of the season on loan at the Buddies.
After his non-stop campaign Gordon could be forgiven for being ready for a chance to rest and recuperate.
But he also reckons the down-time will help Rodgers to impress more of his methods and his philosophies onto the squad.
He said: “Kieran Tierney has played almost the same amount of games as I have. When you add in the internationals it is a lot of football.
“This break will refresh everyone and recharge the batteries.
“But the important thing is it allows the manager to do a bit of work on the training ground too and get a bit of coaching in.
“When there are so many games then you have to recover.
“You have to prepare for the next game and there is not the same chance to do detailed work.
“So this is going to be a good coaching week for the players.
“It will let us refocus and look at the things we are good at and have another think about the way the manager wants us to play.”